1. Field of the Invention
The present invention relates to the field of materials processing equipment, and more particularly to vacuum processing systems for processing a substrate.
2. Discussion of the Background
Plasma processing systems are used in the manufacture and processing of semiconductors, integrated circuits, displays, and other devices or materials to both remove material from or to deposit material on a substrate, such as a semiconductor substrate. In such processes, plasma can be employed to create and assist surface chemistry within such a plasma processing system. It has become standard practice in the semiconductor industry to use plasma processing of semiconductor substrates to perform plasma assisted pattern etching, whereby a pattern for an integrated circuit that is formed in a photolithographic mask is transferred to the substrate, or to perform plasma enhanced vapor deposition, whereby dielectric or conductive films are deposited on the substrate.
In general, plasma is formed with the plasma processing system under vacuum conditions by heating electrons to energies sufficient to sustain ionizing collisions with a supplied process gas. The process gas is introduced via a gas inject plate or a showerhead into the plasma processing chamber, and the process gas is subsequently heated through collisions with energetic electrons in the presence of an electrical field created between an upper electrode assembly and a substrate. The heated electrons can have energy sufficient to sustain dissociative collisions, or sustain ionization collisions. Therefore, a specific set of process gases under predetermined conditions (such conditions include, for example, the chamber pressure, gas flow rate, power, etc.) are chosen to produce a population of charged species and chemically reactive species suitable to the particular process being preformed within the chamber. Such processes can be for example the etching processes where materials are removed from the substrate, or deposition processes where materials are added to the substrate.
It is well known that process uniformity across the substrate surface is important to providing homogeneous device characteristics across the substrate surface and improved manufacturing yields per substrate. For example, a gas injection showerhead is typically implemented in an attempt to provide a uniform distribution of process gas across the substrate surface, thereby improving process uniformity. Despite these efforts, however, process uniformity still remains a problem in processing semiconductor substrates.